Image amplification of negative-working diazo materials

Abstract

A method for the amplification or intensification of dye images formed in a negative-working diazo system which comprises the steps of: (1) initially image-wise exposing a negative-working diazo layer to actinic radiation sufficient to convert a portion of the diazo compound contained therein to an active coupling constituent in the light-struck areas to form a first latent image, (2) developing the exposed diazo layer to effect coupling so as to form colored incipient images in the light-struck areas, (3) exposing the entire diazo layer from the same side as the initial image-wise exposure to actinic radiation of a greater amount than that used in the initial exposure, said amount of actinic radiation being sufficient to substantially photolyze the non-image areas while simultaneously creating second latent images beneath the already-developed areas, and (4) developing the exposed diazo layer again to effect coupling in said second latent image areas to form color therein and to amplify the initial colored incipient images. Further amplification may be obtained by exposing the diazo layer from the side opposite that of the initial exposure and again developing to effect coupling of any remaining diazo under the original dye image areas.

We claim: 
     
       1. A method for the amplification of dye images formed in a negative-working diazo material having a support and a negative-working acid stabilized diazo layer thereon wherein, on continued exposure to actinic radiation, the diazo compound goes through a photolytic transition starting with an unreactable or non-coupling state, to a reactable state, and finally to an unreactable state, the steps of image formation and amplification which comprise: (1) initially image-wise exposing the negative-working diazo layer to actinic radiation sufficient to convert a portion of the diazo compound contained therein to an active coupling constituent in the light-struck areas to form a first latent image, (2) developing the exposed diazo layer by means of an alkaline agent and/or heat to effect coupling so as to form colored incipient dye images in the light-struck areas, (3) exposing the entire diazo layer from the same side as the initial image-wise exposure to actinic radiation of a greater amount than that used in the initial exposure, said amount of actinic radiation being sufficient to substantially completely photolyze the non-image areas while simultaneously creating second latent images beneath the already-developed dye image areas, and (4) developing the exposed diazo layer again by means of an alkaline agent and/or heat to effect coupling in said second latent image areas to form color therein and to amplify the initial colored incipient dye images. 
     
     
       2. The method of claim 1, further comprising the steps of exposing the entire diazo layer after the developing step (4) from the side opposite that of the initial image-wise exposure to actinic radiation approximately equal to that of the initial exposure to convert any unphotolyzed diazo compound remaining under the dye image areas to an active coupling state, and developing the diazo layer exposed under said dye image areas to initiate coupling so as to further intensify said dye image areas. 
     
     
       3. The method of claim 1, wherein the amount of the actinic radiation in step (3) is about 2 to 100 times the amount of actinic radiation used in the initial exposure in step (1). 
     
     
       4. The method of claim 1, wherein said negative-working diazo layer comprises a light-photolyzable diazo compound which is capable of transition to a color-former by photolysis, and an acidic stabilizer on a suitable support. 
     
     
       5. The method of claim 1, wherein said negative-working diazo layer comprises a light-photolyzable inactive diazo compound which is capable of transition to an active diazo form by photolysis, an acidic stabilizer and a coupler on a suitable support. 
     
     
       6. The method of claim 1, wherein said negative-working diazo layer comprises multiple layers coated on a suitable support, one of said layers comprising a light-photolyzable diazo compound which is capable of transition to a color-former by photolysis and an acidic stabilizer and another of said layers comprising a light-photolyzable inactive diazo compound which is capable of transition to an active diazo form by photolysis, an acidic stabilizer and a coupler. 
     
     
       7. The method of claim 1, wherein the concentration of diazo compound in said layer is such that the unexposed diazo compound has an Absorbance in its region of maximum spectral absorption of greater than 1.0. 
     
     
       8. The method of claim 1, wherein said developing is carried out by using an alkaline agent to achieve coupling. 
     
     
       9. The method of claim 8, wherein said alkaline agent is ammonia. 
     
     
       10. The method of claim 9, wherein the diazo layer is heated after the developing step (2) in order to drive off the ammonia. 
     
     
       11. The method of claim 10, wherein the diazo layer is cooled after said heating step and before the exposure of step (3). 
     
     
       12. The method of claim 8, wherein said alkaline agent is a volatilizable amine. 
     
     
       13. The method of claim 12, wherein the diazo layer is heated after the developing step (2) in order to drive off the volatilizable amine. 
     
     
       14. The method of claim 13, wherein the diazo layer is cooled after said heating step and before the exposure of step (3). 
     
     
       15. The method of claim 1, wherein said developing is carried out by using heat to achieve coupling. 
     
     
       16. A method for the amplification of dye images formed in a negative-working diazo material having a support and a negative-working acid stabilized diazo layer thereon wherein, on continued exposure to actinic radiation, the diazo compound goes through a photolytic transition starting with an unreactable or non-coupling state, to a reactable state, and finally to an unreactable state, said diazo compound being selected from the group consisting of diazo oxides, diazo sulfonates, diazosulfones and diazocyanides, the steps of image formation and amplification which comprise: (1) initially image-wise exposing the negative-working diazo layer to actinic radiation sufficient to convert a portion of the diazo compound contained therein to an active coupling constituent in the light-struck areas to form a first latent image, (2) developing the exposed diazo layer by means of an alkaline agent and/or heat to effect coupling so as to form colored incipient dye images in the light-struck areas, (3) exposing the entire diazo layer from the same side as the initial image-wise exposure to actinic radiation of a greater amount than that used in the initial exposure, said amount of actinic radiation being sufficient to substantially completely photolyze the non-image areas while simultaneously creating second latent images beneath the already-developed dye image areas, and (4) developing the exposed diazo layer again by means of an alkaline agent and/or to heat effect coupling in said second latent image areas to form color therein and to amplify the initial colored incipient dye images. 
     
     
       17. The method of claim 16, further comprising the steps of exposing the entire diazo layer after the developing step (4) from the side opposite that of the initial image-wise exposure to actinic radiation approximately equal to that of the initial exposure to convert any unphotolyzed diazo compound remaining under the dye image areas to an active coupling state, and developing the diazo layer exposed under said dye image areas to initiate coupling so as to further intensify said dye image areas.